Automatic reclosing circuit breaker equipment



S. B. CRARY June 2, 1942.

AUTOMATIC RECLOSING CIRCUIT BREAKER EQUIPMENT Filed Deo. 28, 1940 RESPONSIVE T0 FAULTS INVOLVING CONDUCTORIS P0 LYPHASE FDWER RESPONSIVE Patented June 2, 1942 AUTOMATIC RECLOSING CIRCUIT BREAKER EQUIPMENT Selden B. Crary, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 28, 1940, Serial No. 372,103

(Cl. F75-294) Claims.

My invention relates to automatic reclosing circuit breaker equipments and particularly to an equipment for controlling the reclosing of single pole circuit breakers in a polyphase circuit, and one object of my invention is to provide an improved arrangement of apparatus for i reclosing such a single pole circuit breaker after it has been opened by a fault involving the associated line conductor.

As a result of considerable study of single pole switching for the clearing of faults on polyphase lines, I have found that the length of time that a single pole circuit breaker in a polyphase line should be maintained open without resulting in loss of synchronism of the connected rotating apparatus system, in order to provide a maximum factor of safety for deionization of the arcing path and for restriking of `the lightning stroke due to multiple stroke phenomena, varies inversely with the amount of power being transferred over the line at the time the fault occurs. Also in some cases the time that the single pole circuit breakers should remain open before being reclosed depends upon the type of fault, namely whether it is a line to ground, double line to ground, or a three-phase fault.

In accordance with my invention, I provide an arrangement of apparatus for controlling the reclosing of a single pole circuit breaker in a polyphase circuit so that, when a relatively small amount oi power is being transferred at the time a fault, involving the associated line conductor, occurs a much longer time elapses between the opening and the reclosure of the circuit breaker than elapses when a relatively large amount of power is being transferred at the time such a fault occurs. Also in those instances where it is necessary, the length of time that the single pole circuit breaker is maintained open is modified in accordance with the type of fault. For example, for a line to ground fault involving only one conductor, the single pole circuit breaker associated with that conductor involved in the fault may be reclosed after being opened for a different predetermined time interval than when the fault involves that conductor and another.

My invention will be better understood from the following description when taken in connection with the accompanying drawing, the single figure `of which illustrates an automatic reclosing circuit breaker arrangement embodying my invention, and the scope of my invention will be pointed out in the appended claims.

Referring to the drawing, I, 2 and 3 are the three line conductors of a three-phase circuit, and 4, 5 and 6 represent suitable single pole circuit breakers in the line conductors I, 2 and 3, respectively. Each circuit breaker is shown as a latched closed circuit breaker having a closing coil 'I and a trip coil 8. Each circuit breaker also has associated therewith suitable fault responsive means for eifecting the energization of the associated trip coil 8 in response to a fault involving the associated line conductor. Since such fault responsive means are well known in the art and my invention does not relate to the details thereof, I have represented such fault responsive means for the conductors I, 2 and 3 by rectangles III, II and I2, respectively. Each of these fault responsive means includes three sets of contacts I3, I4 and I5 which are closed in response to a fault involving the associated line conductor. The closing of the contacts I3 of each fault responsive means completes an energizing circuit for the trip coil 8 of the circuit breaker in the associated line conductor. The contacts I4 and I5 of the fault responsive means II), II and I2 are interconnected so as to effect the energization of an associated quick acting relay I6 in case any two of the fault responsive means are simultaneously operated in response to a fault involving two or more of the line conductors. The relay I5 is pre-ferably designed in any suitable manner so that its contacts I1 remain closed for a predetermined time after the relay is deenergized. These contacts I'I, when closed, complete an energizing circuit for the closing coil 1 of each circuit breaker, which is then open, so as to effect the immediate reclosing thereof.

In order to eifect the reclosing of a circuit breaker after being opened for a relatively long time interval, when the fault which effects the opening of the circuit breaker involves only the associated line conductor, I provide a time delay relay I8, which is energized in response to the opening of each circuit breaker and which, after being energized for a predetermined length of time, closes its contacts I9 which are so connected that, when they are closed, they complete an energizing circuit for the closing coil 1 of each circuit breaker which is then open.

However, in orde-r to effect the reclosing of a circuit breaker before the time delay relay I8 has completed its timing operation in case the power being transferred at the time a fault involving only the associated line conductor occurs, I provide a three-phase wattmeter 2|), which is connected to the line conductors I, 2 and 3, in any suitable manner examples 0f which are well known in the art so that either contacts 2| or 22, depending upon the direction of power flow through the conductors I, 2 and 3, are closed when the amount of power iiew exceeds a predetermined value. In order to simplify the disclo- Sure, I have represented the wattrneter ZI? merely by a rectangle since the detailed connections vof such a device are well known in the art, and my present invention does not relate to such detailed connections. The contacts 2l Vand 22 are con nected in parallel in an energizing circuit for a time relay 24 so that its contacts 25 are closed after the contacts 2l or 22 have remained closed for a predetermined time limit. The contacts 25; when closed, complete an energizing circuit for the closing coil 'l of any circuit breaker which may be opened at that time.

The operation of the arrangement shown in the drawing is as follows:

When a fault involving only one of the line conductors occurs, the respective fault responsive means operates to effect the opening or the associated circuit breaker. For' example, upon the occurrence of a faultinvolving only the line conductor I, only the fault responsive ymeans I operatesto close its contacts I3, It and It.V The closing of the contacts I3 oi the fault responsive means IE! completes an energizing circuit for the trip coil 8 of the circuit breaker i so as to effect the opening thereof. As soon as the circuit breaker'd opens, its auxiliary contacts 21 complete anv energizing circuit for the time delay relay I8, but this relay does not close its conn tacts I9 until a predetermined time after the relay I8 is energized. When the relay I8 closes its contactsy I 9, a circuit is completed for the closing coil I of the open circuit breaker I through the auxiliary contacts 2S thereof to eirect the closing of the circuit breaker d.

If at the time the fault involving only the line conductor I occurs, the power being transferred is above a predetermined value so that one o f the two sets of contacts or the relay 2t has been closed long enough to cause the contacts 25 of therelay Z4 to be closed, the circuit 0f the closing coil I ofthe circuit breaker 4 is closed as soon as the auxiliary contacts 28 of the circuit breaker 4 are closed, and this occurs before the time relay I8 completes its timing operation. Therefore, it will be seen that, if the power being transferred through the conductors I, 2 and 3 is above a predetermined value when a fault occurs which involves only one line conductor, the circuit breaker associated with the faulty line conductor is Vimmediately reclcscd whereas if the power is below this predetermined value when the fault occurs, the circuit breaker is notreclosed until after it has remained opened for a relatively long predetermined time interval.

When a fault involving more than one line conductor-occurs, the fault responsive means associated with each of the involved line conductors closes its respective contacts I3, I 4 and I5.

'For example, if the fault involves both of the conductors 2 and 3, the fault responsive means VII and I2 close their respective contacts I3, I4

and I5. The closing of the lcontacts I3 of the fault responsive means II completes an energizing circuit for the trip coil 8j of the circuit breaker 5, and the closing of thev contacts I3 of the fault responsive means I2 Vcompletes an energizing circuit' for the trip coil ii of the circuit breaky er 6 so that both of these circuit breakers are openedf Also an energizing circuit is completed for the instantaneous relay i@ through the con- Cil sociated with the involved line conductors are l immediately reclosed irrespective of the amount of power being transferred at the time the fault occurs.`

While I have, in accordance with the patent statutes, shown and described my invention as applied to a particular system and as embodying various devices diagrammatically indicated, changes and modications will be obvious to those skilled in the art, and I therefore aim in the appended claims to cover all such changes and modifications as'iall within the truerspirit andy scope of my invention( `vWhat I claim as new and desireto secure b Letters Patent of 'the United States is l. In combination, Va polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuit, means for opening each breaker in response to a fault involving the associated phase conductor, and means for re- 'closing a circuit breaker after aV time interval whichdep'ends upon the number of phase conductors involved in the fault.'

2. In combination, a polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuit, means for opening each breaker in response to a iaultlinvolving the associated phase conductor,"and means for reclosing a circuitrbreaker after a time interval which depends upon the amount of polyphase power being transferred when the fault occurs.

3. In combination, a pclyphase circuit, a single Vpole circuit breaker in series with each phase conductor of said circuit, means for opening each ,breaker` in response to a fault involving the associated phase conductor, and means for reclosing a circuit breakeraiter dilerent time intervals dependent upon the amount of polyphase power being transferred when the fault occurs.

4. In combination, a polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuit, means for opening each breaker in'response to a fault involving the associated phase conductor, and means for reclosing a circuit breaker after a relatively short time interval when the amount of power being transferred when the fault occurs exceeds a predetermined amount and after a relatively long time interval when the amount of power being transferred when the fault occurs is less than said predetermined value.

5. In combination, a polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuity means for opening each breaker in response to a fault involving the associated Vphase conductor, means for reclosing a circuit breaker after a time interval dependent upon the amount of power being transferred when the fault occurs, and means for reclosing a circuit breaker after a different time interval which depends upon the number of conductors involved in the fault. i

6. In combination, a polyphase circu-it,'a single pole circuit breaker `vin series with each phase conductor of ysaidcircuit, Ymeans for opening each breaker -in response to a fault involving the associated phase conductor, means for reclosing a circuit breaker after a predetermined time interval when the amount of power being transerred when the fault Occurs is less than a predetermined amount, means for reclosing a circuit breaker before the expiration of said predetermined time interval when the amount of power being transferred when the fault occurs is above said predetermined value, and means for reclosing a circuit breaker before the expiration of said predetermined time interval when the fault involves more than one conductor of said circuit.

'7. In combination, a polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuit, means for opening each breaker in response to a fault involving the associated phase conductor, and means for reclosing a circuit breaker after a predetermined time interval when the amount of power being transferred when the fault occurs is less than a predetermined amount and before the expiration of said predetermined time interval when the amount of power being transferred when the fault occurs is above said predetermined value.

8. In combination, a polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuit, means for opening each breaker in response to a fault involving the associated phase conductor, and means for reolosing a circuit breaker after a predetermined time interval when the amount of power being transferred when the fault occurs is less than `a predetermined amount and before the expiration of said predetermined time interval when the fault involves more than one conductor of said circuit.

9. In combination, a polyphase circuit, a single pole circuit breaker in series with each phase conductor of said circuit, means for opening each breaker in response to a fault involving the associated phase conductor, and means for reclosing,r a circuit breaker after a predetermined time interval when the fault involves only the associated circuit conductor and before the expiration of Said time interval when the fault involves more than one circuit conductor.

10. In combination, a polyphase circuit, a single pole circuit Vbreaker in series with each phase conductor of said circuit, means for opening each breaker in response to a fault involving the associated phase conductor, and means for reclosing a circuit breaker after different time intervals dependent upon the number of circuit conductors involved in the fault.

SELDEN B. CRARY. 

